The present invention generally involves an apparatus and method for supplying fuel to a gas turbine. Specifically, the present invention describes a nozzle that may be used to supply fuel to a combustor in a gas turbine.
Gas turbines are widely used in industrial and power generation operations. A typical gas turbine includes an axial compressor at the front, one or more combustors around the middle, and a turbine at the rear. Ambient air enters the compressor, and rotating blades and stationary vanes in the compressor progressively impart kinetic energy to the working fluid (air) to produce a compressed working fluid at a highly energized state. The compressed working fluid exits the compressor and flows through nozzles in the combustors where it mixes with fuel and ignites to generate combustion gases having a high temperature, pressure, and velocity. The combustion gases expand in the turbine to produce work. For example, expansion of the combustion gases in the turbine may rotate a shaft connected to a generator to produce electricity.
It is widely known that the thermodynamic efficiency of a gas turbine increases as the operating temperature, namely the combustion gas temperature, increases. However, if the fuel and air are not evenly mixed prior to combustion, localized hot spots may form in the combustor near the nozzle exits. The localized hot spots increase the chance for flame flash back and flame holding to occur which may damage the nozzles. Although flame flash back and flame holding may occur with any fuel, they occur more readily with fuels that have a higher reactivity, such as hydrogen, that have a higher burning rate and wider flammability range. The localized hot spots may also increase the production of nitrous oxides, carbon monoxide, and unburned hydrocarbons, all of which are undesirable exhaust emissions.
A variety of techniques exist to allow higher operating temperatures while minimizing localized hot spots and undesirable emissions. Nevertheless, the risk of fuel leaks, as well as the damaging flame flash back and holding, that usually results from such leaks, remain a significant industry concern. These issues also exist in so-called “micromixer” fuel nozzles because each nozzle employs a number of separate “micro” mixing-tubes so to produce a more uniform fuel/air mixture for combustion. As one of ordinary skill in the art will appreciate, a more uniform fuel/air mixture offers several performance advantages. However, known design configurations of these type of fuel nozzles are less than ideal. The multiple tubes and more complicated arrangement has resulted in a fuel nozzle that is expensive to manufacture and susceptible to fuel leakage and the damaging flashback and flame holding that typically comes with such leaks.
As a result, novel designs that simplify these types of fuel nozzles, while still achieving the performance advantages associated with the improved premixing of the fuel and air, would be prized in the marketplace. Specifically, new designs that allow for a more robust, cost-effective fuel nozzle that decreases the likelihood of leaks while also limiting the damage that typically attends such leaks when they occur, would represent a meaningful advancement in this technological area.